Tanning material



Patented o r. 22, 1940 PATENT OFFICE TANNING MATERIAL Arthur Voss andWalter Pense, Frankfort-on-the Main-Hochst,. Germany, assignors, bymesne assignments, to General Aniline 8; Film Corporation, New York,Delaware N. Y., a corporation of No Drawing. Application November 26,1937, Se-

rial No. 176,714. In Germany December 2,

"4 Claims,

The present invention relates to tanning materials.

Numerous synthetic tanning materials are known which are made byproducing in a watersoluble form bodies of of the aromatic series.

a high molecular weight By bodies of a high molecular weight there areto be understood in most cases bodies which are at least binuclear;

for instance naphthalenesulfonic acid has hardly any tanning action,whereas trinuclear bodies have already a highdegree of tanning action.Sulfonic acids with distinctly good tanning properties are known; theyare in particular obtained by condensing the sulfonated aromatic nucleiwith formaldehyde and thus connecting them by one or more methylenebridges. These tanning materials have the special property of producinga plumping action on the leather, but this action is not sufiicient whenthe products are usedas the sole tanning material, that-is without theaddition of vegetable tanning materials have a plumping efi'ect.

In order to imitate vegetable tanning materials as much as possible, theattempt has been made to combine tanning substances which have noplumping effect and yield flat leather, with phlobaphene-like bodies,namely bodies which are themselves insoluble in water. As bodies of thiskind there are preferably used condensation products of phenols andaldehydes, because they can readily be brought into a water-soluble formwith the aid .of the non-plumping sulfonic acids by a process ofpeptization or condensation. Al-

ready in this water-soluble form they yield relatively well plumpedleather.

Now we have found that the plumping effect of tanning materials of thiskind may considerably be increased by the process described below:

Instead of combining the non-plumping tanning materials withphenol-aldehyde-condensation products insoluble in water, they arecombined with phenol-aldehyde condensation products which have already acertain solubility in water, but so small a solubility that they are notsuitable of themselves to transform pelt by the usual tanning processinto a useful leather. More exactly defined, there are usedphenol-aldehyde condensation products which are not soluble in water toa clear solution in a concentration suitable for'the tanningliquors ofthe usual concentration. There are used products which are soluble inwater only in too large a dilution or which are'soluble only in hotwater but separate again at ordinary temperature. They are soluble to aclear solution only in an alkaline agent. When combined with vegetableextracts they tend to precipitate so that in this combination they arelikewise unsuitable as tanning materials,

Bodies of this kind may be obtained, for instance, from products of thecondensation (which may be carried out in an acid or an alkaline medium)of phenol, ortho-, meta or paracresol or of 'a commercial cresolmixture, of xylenols or of naphthols with formaldehyde or acetaldehyde.Suitable parent condensation products are also dihydroxy-diphenylmethaneor dihydroxy-diphenylethane. For converting these condensation productsinto bodies useful for the purpose of the invention, the condensationproducts are sulfonated in'such a manner that only so many sulfo-groupsare introduced as are necessary fortheproperties above referred to. Theproportion of the sulfo-groups is kept so low that 4 aromatic nucleicorrespond with at most one sulfa-group. Such partly sulfonatedcondensation products are obtained by treating for instance acondensation product of phenol and aldehyde only for so long a time oronly with such a quantity of concentrated sulfuric acid, or anequivalent sulfonating agent, that not more than about 6 per cent. ofsulfur is contained in the purified and isolated tanning material. Thesulfonation is preferably performed in the presence of a diluent. Orthe. sulfonation is carried out with the aid of sulfite by condensingfor instance phenol with formaldehyde and sodium sulflte in a proportionthat for one mol of phenol at most. mol of sodium sulfite is used.Suitably the content of sulfur in the products should not be below 5 percent, for the products then become too sparingly soluble in water. V

As peptizing components there are used they known aromatic sulfonatedhydrocarbons or phenols of high molecular weight. Such sulfonic acidshaving more or less tanning action are obtained by the sulfonationofphenol, cresol, naphthalene, alkvlated or aralkylated naphthalene, ifnecessary'with a subsequent condensation with for instance formaldehyde.There may also be used sulfo-compounds into which a non-sulfonatedphenol-condensation product has already been condensed or peptized. Theprocess is'for instance carried out as follows: naphthalene su1- fonicacid'is condensed or peptized at about o C. with a certain quantity of aresinous body obtained from phenol andformaldehyde, this body beingsubstantially insoluble in water, until a product is formed which issoluble inwater to a clear solution. This product is mixed with a 55product obtained by heating together for several hours cresol,formaldehyde and sodium sulflte in uch proportion that for 1 mol ofcresol about t e equivalent quantity of formaldehyde and only half theequivalent quantity of sodium sulflte are used. As peptizing componentthere may also be used waste sulfite liquor.

The quantitative proportions of the peptizing component and of thecomponent sulfonated so as to contain only at most 6 per cent. of sulfurmay vary within wide limits according to the character of the tanningmaterial and the plumping effect to be attained. When using a weaklysulfonated component sparingly soluble in water it is advantageous touse a large quantity of the .peptizing component.

The technical improvement which is the result of the process consists inthe following: with the aid of the process it is possible to obtaintanning materials having a much larger proportion of substances of aplumping action (phlobaphenes) than has hitherto been usual; that it,,itis possible to prepare tanning materials having properties which areequal to those of the vegetable tanning materials not only with regardto the plumping action but also in view of the firmness and solidity ofthe leather. Moreover, this effect is attained in a particularlysimplemanner. As compared with the introduction of a waterinsoluble phenolcondensation product by peptization or condensation, the presentinvention has the advantage, apart from the improved properties, that itis not necessary to attain the formation of a uniform product, such asis necessary for a useful tanning process, by a complicated condensationor peptization; on the contrary the components are simply mixed atordinary temperature and a tanning material 'having the propertiesdescribed is thereby obtained.

The new tanning materials may also be combined with known vegetabletanning materials such as for instance quebracho or sumach.

The following examples serve to illustrate the invention, but they arenot intended to limit it' u thereto; the parts are by weight:.

1. 110 parts of a condensation product "of the novolak type from cresoland formaldehyde are dissolved in 180 parts of anhydrous pyridine andparts of chlorosulfonic acid are caused to run into the solution'in thecourse of about 20 minutes at alow temperature (0 C. to 5 0.). The massis then stirred for some time'at ordinary temperature (about 20 C.) Thesolid product contains between about 5 per cent and about 6 per cent ofsulfur. As soon as a test portion dissolves in water to a clearsolution, the fusedmaterial is mixed with 300 parts of water and such aquantity of caustic soda solution that the reaction of the solutionobtained is just distinctly alkaline to phenolphthalein. The pyridine isthen eliminated by blowing steam directly into the solution. Onacidifying the solution of the weakly sulfonated phenol resin aresinous'precipitate is formed which, after removal of the -may directlybe used for tanning. A full bodied leather is obtained.

2. 100 parts of cresol (commercial), '70 parts of formaldehyde and 55parts of sodium sulilte (crystallized) are mixed and the mixture is keptgently boiling for about 8 to 10 hours, while continuously stirring.When a test portion of the syrupy mass is soluble in water to a clearsolution, acidification of the aqueous solution precipitates a resinwhich can be redissolved in hot water free from the electrolyte;according to the concentration of the solution the resin separates againmore or less completely in the cold. The solid product contains betweenabout 5 per cent and about 6 per cent of sulfur.

The condensation product thus obtained is mixed with a sulfonationproduct which has been obtained as follows:

A mixture of '75 parts of phenol and parts of concentrated sulfuric acidis kept for 2 hours at 100 C. to 105 C.; after the mass has been allowedto cool to 30 C. to 40 C. 30 parts of formaldehyde (of 30 per cent.strength) are caused to run in within half an hour at this temperature,while well stirring; during this operation the viscosity of the massconsiderably increases; the mass is then kept for a further half hour at50 C.

The mixture of the two sulfonation products has an acid reaction; it issoluble in water-to a clear solution. By the addition of the quantitytity of alkali as is required for attaining the acidity suitable fortanning purposes, a tanning solution is obtained, with the aid of whichleather -of water required for tanning and such a quanmay be producedwhich is of full body and of good firmness and solidity. An addition ofvegetable extract is not necessary even when making sole leather.

3. parts ,of the dihydroxy-diphenyl-dimethyl-methane obtained bythe'condensation of phenol and acetone are introduced at 65 C. to 70 C.,while stirring well, into 150 parts of a crude mass oftetrahydronaphthalene-sulfonic acid obtained by the sulfonation of 130parts of tetrahydronaphthalene by means of 110 parts of anhydride; 35partsof concentrated sulfuric acid are then introduced into the viscoussolution at ordinary temperature, while well stirring.

After the whole has been introduced, the temperature is kept at C. forone hour or until at test portion of the mass is soluble in hot waterto'a clear solution and separates again in the cold. The solid productcontains between about 5 per cent and about 6 per cent of sulfur. Theweakly sulfonated phenol resin thus obtainedis mixed with thesulfonation component first named. The mixture is a homogeneous andviscous mass which is soluble in water to' a clear solution. The leathertanned therewith is of full body. The sole leather made with thisproduct is not, inferior to that obtained with the aid of the vegetabletanning agents.

4. parts of cresol (commercial) are sulfonated with parts ofconcentrated sulphuric acid and into the sulfonation mixture thusobtained there are introduced at 60 C. to 70 C.

80 parts of a condensation product of 20 parts of e-naphthol, 40 partsof cresol and 35 parts of formaldehyde of 30 per cent. strength; inorder to obtain the said condensation product the constituents named aremixed with 4 parts of sodium parts of cresol, 80 parts of formaldehydeand 60 parts of sodium sulfite. The mixture is a highly viscous syrupysubstance, which dissolves in water to a clear solution and, like thetanning matters described above, is very well suitable for tanning soleleather without an addition of vegetable tanning material.

We claim:

1'. As new tanning agents mixtures containing a sulfonated condensationproduct of a-phenol with an aldehyde, said condensation product beingobtained by sulfonation by means of asulfite and containing at mostabout 6 per cent. of sulfur, and a known synthetic tanning agent of thegroup consisting of sulfonated aromatic hydrocarbons and phenolsof-high' molecular weight.

2. As new tanning agents mixtures containing I said condensation productbeing obtained by sulfonation by means of a sulfite and containing atmost about 6 per cent. of sulfur, and a known synthetic tanning agent ofthe group consisting of sulfonated aromatic hydrocarbons and phenols ofhigh molecular weight.

3. As new tanning agents mixtures containing a sulfonated condensationproduct of a phenol with an aldehyde, said condensation product beingobtained by sulfonation by means of a sulfite and containing at leastabout 5 per cent. and at most about 6 per cent. of sulfur, and a knownsynthetic tanning agent of the group consisting of sulfonated aromatichydrocarbons and phenols of high molecular weight.

4. As a new tanning. agent a mixture of a sulfonated watersoluble acidcondensation. product of phenol. and formaldehyde with a sulfonated'cresol-formaldehyd-e condensation product containing between about 5per cent. and about 6 per cent. of sulfur and obtained by gently boilinga mixture of cresol, formaldehyde and crystalline sodium sulfite forabout 8 to 10 hours.

ARTHUR VOSS. WALTER PENSE.

